The island was formed in three distinct
phases. The first phase was the emergence of the island
from below the sea by massive volcanic eruption. The second
and third phases combined high volcanic activity followed
by erosion, during which time the northern plains and
the northern shelf islets of Gunners Quoin, Flat, Gabriel
Islands, Round and Serpent islands were formed. At this
time the sea levels were 100 m lower and these northern
islets formed part of the northern plain system.
Geography
Mauritius is 58 km from north to south and 47 km from
east to west with an area of 1865 km2. The other island
dependencies of Mauritius include, Rodrigues 600 km to
the east, St Brandon (Cargados Carajos) 460 km to north
east and Agalega 1200 km to the north. Reunion lies approximately
220 km and Madagascar 800 km to the west of Mauritius.
The topography of the island consists of a central plateau
which rises dramatically to the south west with the highest
point being Piton de la Petite Riviere Noire at 828 m.
The central plateau is surrounded by the remnants of the
primary volcanic crater system, including the second highest
pint of Pieter Both at 823 m (the one with the boulder
on top). To the north the island drops and flattens out
to form the extensive northern plains extending down the
west coast of the island as a coastal plain. The east
coast has a very narrow to non existent coastal plain
with relatively steep topography rising from the coast.
The longest river on the island is the Grand Riviere Sud
Est which is 34 km from its head waters in the central
plateau to where it enters the sea near Ile aux Cerfs.
Formation of the Coral Reef in Mauritius
In Mauritius corals started to grow in shallow waters
parallel to the shore resulting in the formation of a
fringing reef, covering 150 Km around the coast of Mauritius.
In the south east, at Grand Port/Mahebourg, there is a
short stretch of typical barrier reef, while there are
no reefs on the south coast. In geological terms a fringing
reef is a relatively young reef. Fringing reefs protect
the shoreline and the coral and seagrass habitats that
develop within the lagoon. Reefs are very complex with
different shaped corals forming ecological niches.
36 Genera and 90 species of hard corals have been recorded
in the waters of Mauritius. Growth rates of coral colonies
vary from 0.5 cm – 7 cm per annum and a football
size coral head takes approximately 50 years or more to
grow. As the coral colonies grow, the remaining skeletal
forms of the organisms consolidate forming coral bedrock
that is the foundation of the reef. The growth rate of
a reef platform is dependent on environmental factors,
but it is generally accepted to be around 1 cm per year.
However corals are fragile and can be easily impacted
and broken. As the living structure of the reef platform
is broken down by trampling, pollution, or other impacts,
the height of the reef platform is lowered exposing the
lagoon habitats and the shoreline to excessive wave action
which they are not designed to withstand, often contributing
to shoreline erosion.
Impacts on the lagoon and coral reefs
of Mauritius
The impacts on the lagoons and coral reefs of Mauritius
have been chronic and intense, starting 400 hundred years
ago with the demise of the native forests, resulting in
chronic sedimentation in the lagoons. Massive clearing
of land for sugar plantations brought with it further
sedimentation and associated pesticides and fertilisers
being washed into the lagoons. The filling in of what
were extensive wetlands which act as important natural
filters has had severe impacts on the lagoons with polluted
run off water directly entering the lagoon. Sand extraction
for the construction industry caused more sedimentation
and erosion of the seagrass beds. Excessive sedimentation
results in poor light quality, inhibiting coral growth
and can also smother the coral, killing the colonies.
Uncontrolled coastal and industrial development with associated
pollution, dynamite fishing and other negative forms of
fishing such as the seine nets have all contributed as
long term stressors on the lagoons and reef systems.
Tourism also has its direct and associated impacts, with
snorkel and dive boats dropping anchors and breaking the
coral, collection of shells and corals for sale to visitors
has depleted the number of shells and people holding,
walking and sitting on coral all contribute to the demise
of the lagoon habitats the visitors have come to see.
Today, many of these impacts are being addressed. Sand
extraction is no longer legal, although it still goes
on. Pollution controls are being put in place including
urban sewage systems and there are laws governing coastal
development, new construction must be stepped back a stipulated
distance from the high water mark and not exceed two stories
– however it is not always clear in all cases that
these regulations are being enforced. It is illegal to
collect coral and shells in Mauritius, but it is legal
to import from elsewhere, making it impossible to enforce
the local law and merely displaces the problem from Mauritius
to other countries such as Madagascar, Philippines and
Indonesia. Dynamite fishing no longer takes place and
the placing of Fixed Mooring Buoys on popular dive sites
and (eventually) snorkel sites will protect corals from
anchor damage, but there is still work to do to ensure
that the tourism industry does not continue to destroy
the very habitats that it is so dependent on.
The Days of the DODO
For the Dutch seamen under Van Warwyck in 1598, Mauritius
was a paradise. A first description of Mauritius in 1598
based on this expedition was published in 1601. Quoting
the descriptions from this book gives a clear indication
of how the island was;
‘the country is mountainous
and is covered with green forests of mostly wild trees,
in the midst of which there are palm trees. The soil is
rocky everywhere; it is covered with trees that grow so
closely together that one can hardly move between them.
The wood of those trees is of the finest ebony ever seen,
as black as tar and may be polished like ivory….There
is another type of wood, dark red in colour and yet another
which is yellow as wax. There is a large quantity of palm
trees which have provided the fleet with excellent refreshment.
The head after being cut reveals a sort of marrow inside
that is white and soft as a turnip but brittle –
it is eaten raw and can be prepared as a salad’.
This is likely one of the first descriptions of the Palm
Heart salad.
‘The sea was so full of fish that, at first try,
with the men using the large fishing net, half a ton were
captured, so much so that it was difficult for the net
to be pulled back as it was so full of fish. Those species
of fish not be found in the United Provinces except the
eels and perches. A ray was captured that was quite sufficient
to provide two meals for the entire crew of one ship.
We found many tortoises, some of which were so big that
four sailors could stand on each of them while they kept
moving about. Their shells were so large that six men
could sit on each of them. There are so many birds, including
a large number of turtle-doves, that the sailors killed
up to 150 in one afternoon, and if they could have carried
back even more with them, they would have taken by hand
or by using sticks as many as they would have wanted.
There were also many herons, but it was impossible to
approach them. There was a small number of wild geese
and also many grey parrots. In addition there were birds
which were as large as swans. Each of them had a large
head on which a patch of skin formed a sort of hood; they
had no wings, in the place of which were four to five
black feathers, and for a tail, they had four or five
curled greyish feathers’. This was the description
of the dodo.
The word Dodo is believed to be of Portuguese origin
–
doudo meaning stupid or foolish in Portuguese,
probably reflecting the opinion that the Portuguese seamen
had of the bird that by all accounts was particularly
easy to catch. By reputation, it was apparently a fatty
bird with a foul taste. Despite its apparent bad taste,
(the Dutch called the dodo Walg-vogel, the ‘distasteful
bird’) the Dutch continued to kill the bird in large
numbers, salting them for stores and eating the small
portions such as the stomach and gizzard that were considered
to be tasty, discarding the rest of the bird. Only some
years after the first recorded contact with man, the dodo
was extinct, famous for the rather dubious honour of being
the first recorded species in what has become a long line
of species to suffer extinction. However, it has been
speculated that it was the introduction of the pigs, rats
and cats that brought about the final demise of the dodo,
not necessarily direct over exploitation by man.
Already by 1601 large numbers of rats had been noted
by passing voyagers and yet the island was not settled
by the Dutch until 1638. Such an influx of invasive
species such as rats, cats and pigs must have had massive
yet unrecorded impacts on the natural biodiversity of
the island – perhaps the dodo was only the tip
of the iceberg.
It should be noted that cyclones were named in alphabetic
order, so for example Kalunde was the eleventh cyclone
to have been recorded and monitored in the area.
